Spinal fixation systems may be used in surgery to fix, adjust, and/or align the spinal column. One type of spinal fixation system employs a spinal rod for supporting the spine and fixing, adjusting, and/or aligning the spinal column into the desired orientation. Attachment of the spinal rod to the spinal column has been achieved using a variety of vertebral anchors. Vertebral anchors include screws, hooks, pins, and bolts used to engage the vertebrae and connect the spinal rod to different vertebrae.
The length and diameter of the spinal rod depends on the size and number of vertebrae to be held in a desired position by the spinal fixation system. The size of the spinal rod also depends on the region of the spine where the spinal fixation system is used. For example, in the cervical region of the spine, where the vertebrae tend to be smaller, a relatively smaller spinal rod is used. Conversely, in the thoracic region, where heavier loads are experienced and the vertebrae tend to be larger, a spinal rod having a relatively larger diameter is used. The cervico-thoracic junction of the spine is typically instrumented using spinal rods of two different diameters to accommodate anatomical differences between the cervical and thoracic spine regions. To accommodate a spinal fixation system including spinal rods having different sizes and configurations, a rod connector may be used to join a first spinal rod and a second spinal rod together. The rod connector may be a side-by-side connector, where the ends of the two spinal rods are placed side-by-side and connected using a connector that spans the two ends, or an axial connector, which aligns the axes of the two spinal rods and connects the ends of the spinal rods together along the axial direction. The plurality of possible spinal rod diameters in combination with the plurality of connector arrangements results in a surgeon typically requiring a vast array of connectors on hand in preparation for a given spinal surgery.
The spinal rods in a spinal fixation system may necessarily be bent to conform to a desired curvature of the spinal column in one or more of the anatomic planes as part of a spinal fixation or corrective surgery. Attachment of spinal rods to vertebral anchors such as screws, hooks, pins, and bolts may be complicated by differing curvature of the untreated spine and the curvature of the spinal rod. Instrumentation to force the spinal rod into engagement with the vertebral anchors may be used. Challenges arise in utilizing instrumentation to force the spinal rod into engagement with the vertebral anchors because the instrumentation generally must be releasably affixed to a previously implanted vertebral anchor and the locking mechanism on the vertebral anchor must be engaged while maintaining the spinal rod in the correct position. Simple engagement of the instrumentation with the vertebral anchor is desirable.